# Phase 4: Combined Threshold Model (OADR@20 + Income + OECD)

| DV | Z₁ | Z₁×OADR20 | Z₁×High | Z₁×OECD | N | R² |
|---|---|---|---|---|---|---|
| ca_gdp | 7.266 | 2.729 | 82.130** | -113.520* | 7624 | 0.057 |
| gross_savings_gdp | 133.517*** | -0.813 | -28.069 | -98.712 | 6642 | 0.185 |
| gross_investment_gdp | 40.972*** | -4.328 | -16.045 | -0.417 | 6620 | 0.074 |
| nfa_gdp | 0.575 | 0.598 | -9.016** | 8.977 | 7712 | 0.128 |

*Combined model tests whether OADR aging threshold, income level, and institutional development independently moderate Z₁.*
